Depending upon the location of the sewage treatment plant, municipalities rely upon gravity, or mechanical means such as pumps, or both, to move fluid waste materials through a sanitary sewer system. The pumps used to move the waste materials may range in size from 10 horsepower to 500 horsepower, and pressures of upwards of 100 psig, or more, may be required to maintain flow in the conduits comprising the system. Due to the nature of fluid waste materials, they manifest a high fluid flow friction loss, or drag, during transport in a sewer system. This problem can become acute when the system is overloaded during periods of heavy use, or when the conduits of the system are too small to handle the volume of fluid waste material entering the system, a condition that oftentimes occurs when a community experiences a substantial growth in population and reaches a point where the original sewer system is no longer adequate to handle the increased demands placed upon it. In order to compensate for the drag which characterizes fluid waste materials, pumping requirements, and, therefore, the cost of moving the materials through the conduits of a sewer system, are correspondingly greater.
It is known that high molecular weight polymers are useful as drag reducing agents in the transportation of fluids through conduits. Thus, for example, in U.S. Pat. No. 4,236,545, radiation polymerized monomers such as acrylamide, methacrylamide, acrylic acid, methacrylic acid, and alkali metal salts thereof, and copolymers of said monomers, are disclosed as being useful as drag reducing agents when incorporated into fluids, especially fluids comprising water and a hydrocarbon. The patent cites a number of other U.S. patents directed to various polymers useful, for example, as drag reducing agents in drilling operations and the transport of oil through pipelines. One of those cited patents, namely, U.S. Pat. No. 3,542,044, discloses the use of an aqueous solution of a partially hydrolyzed polyacrylamide in an oil pipeline for reducing energy loss.